Coronary atherosclerotic plaque composition and classification in hypercholesterolemic pigs.

Rapacz pigs with familial hypercholesterolemia (FH pigs) fed with high-fat diet (HFD) develop early atherosclerotic lesions and complex atheromas in coronaries mimicking human coronary atherosclerotic disease (CAD). FH pigs have proven to be an excellent model for basic and pre-clinical atherosclerosis-focused research. However, unlike human atherosclerosis there has been no established classification system for porcine atherosclerosis. We isolated 104 plaque-containing coronary fragments from atherosclerotic FH pigs. A set of indices (features) of vessel and plaque morphology were quantified for each plaque, including intima-media ratio, vessel size, necrotic core area and fibrous cap thickness. Multifeatured clustering algorithm identified 4 clearly distinguishable plaque groups (A-D). Plaque cellular composition was assessed by immunohistochemistry to quantify relative level of smooth muscle-like, endothelial-like and macrophage-like cells. Plaque neovascularization, collagen levels, calcification and features of vulnerable plaque were assessed and used as additional numerical criteria for plaque classification and to establish the similarity of porcine plaque to specific types of human lesions. Our results indicate that porcine plaque type A, B, C and D correspond to human type III (intermediate lesion), type IV (atheroma), type V (fibroatheroma) and type VI (high-risk vulnerable plaque), respectively. Overall, our data demonstrates the suitability of using the FH pig as a pre-clinical model of human-like coronary atherosclerosis with great potential to advance emergent research in the field of CAD, especially in study of vulnerable plaque and in discovery research.

Background: Animal models facilitate study of coronary atherosclerotic disease. Currently, there is no formalclassification of coronary plaques in the animal models. Pigs are the FDA-preferred species for testing cardiovascular devices and the primary choice for preclinical toxicological testing of anti-atherosclerotic drugs.Pigs with familial hypercholesterolemia (FH pigs) fed with high-fat diet develop early atherosclerotic lesions and complex atheromas in coronaries mimicking human disease and FH pigs are a gold standard model for translational atherosclerosis research. Methods: We isolated 104 coronary fragments from FH pigs. Intima-media thickness ratio, vessel size, necrotic core (NC) area and fibrous cap (FC) thickness were used as morphological criteria to classify plaques by K means clustering. Levels of cell type markers (α-smooth muscle actin, smooth muscle cells, SMC; scavenger receptor type A, SRA, macrophages, MF; CD31, endothelial cells, EC) were quantified by IHC. Intraplaque neovascularization, collagen levels (Trichrome staining), calcification (Von Kossa stain) and intraplaque hemorrhage (Carstairs method) were used as additional criteria and to establish the similarity of porcine plaque to human lesions. Results: We identified 4 clearly distinguishable plaque groups (A-D) in porcine coronary arteries. Plaque group A has no FC and NC, high level of SMC (>18%, as normalized per plaque area) and low MF level (<10%) consistent with the definition of intermediate (type III) human lesions in accordance with the AHA-developed histological classification of human coronary plaques. Group B has small NC area (<15%), thick FC, and large amount of intracellular lipid droplets in intima like type IV atheroma. Group C has increased vessel size (1.6-fold increase vs. group A and B, P<0.05), marked thinning of the tunica media, and a high level of collagen (>43%) mimicking type V fibroatheroma. Group D has a low level of SMC (<7%), high MF content (>15%), large NC area (>30%), multiple breaks in the endothelial layer, severe calcium deposition and neovascularization, and high vulnerability index consistent with type VI complicated lesion. Conclusions: Our results establish the suitability of hypercholesteremic pigs as a pre-clinical model closely mimicking human coronary atherosclerosis and provide researchers with an instrument to study mechanism of atherosclerosis and to assess changes in specific lesion phenotype induced by interventions.

The aim of the present study was to compare the diagnostic values of ultrasound micro-flow imaging (SMI) and contrast-enhanced ultrasound (CEUS) for neovascularization in carotid plaques, and to investigate their capacities for predicting the risks of cerebral stroke. A total of 39 patients (64 carotid plaques) with severe carotid artery stenosis undergoing carotid endarterectomy were selected between February 2015 and February 2016, and SMI and CEUS were used to detect neovascularization in plaques. According to the CEUS dynamic graph of plaques, the enhanced intensity visual scales and contrast parameters were obtained. Carotid atherosclerotic plaques were divided into 4 groups. The differences in the enhanced intensity visual scales, contrast parameters, and gray-scale median (GSM) values among the 4 groups were analyzed. Carotid plaque tissue samples from patients were stained for CD34, and the consistency of the methods for the diagnosis of neovascularization in plaques was analyzed. The differences in GSM values, enhanced intensities, and enhanced densities among the 4 groups of plaques were statistically significant (F=29.365, χ2=29.025, χ2=30.871, P<0.001); the differences in enhanced intensities of carotid atherosclerotic plaques with different echo types were statistically significant (χ2=17.951, P<0.001). The enhanced intensity of plaques was negatively correlated with the GSM value (r=−0.376, P<0.01), and the enhanced density of plaques was negatively correlated with the GSM value (r=−0.252, P<0.01). SMI and CEUS grading had good consistency (κ=0.860>0), there were statistically significant differences in new vessel densities with different SMI gradings (P<0.001), and the clinical symptoms and severity were positively correlated with SMI grading (rs=0.592>0). In conclusion, SMI and CEUS have good consistency for evaluating neovascularization in carotid plaques, and have good clinical value for evaluating neovascularization in carotid plaques.

To study the relationship between serum levels of some inflammatory markers and stability of carotid plaques in the patients with carotid plaques and evaluate the ability of each serum marker in identifying vulnerable carotid plaques. The study included 65 consecutive patients with carotid plaques confirmed by imaging examinations from March 2008 to March 2010. All the patients were classified as stable plaques group (n = 21) and unstable plaques group (n = 44) according to the characteristic findings of the plaques in MRI such as the thickness of fibrous cap, the existence of large lipid core and the intra-plaque hemorrhage. The patients of unstable plaques group were further classified as unruptured plaques group (n = 29) and rupture plaques group (n = 15) according to the integrity of fibrous cap. Serum levels of soluble cluster of differentiation 40 ligand (sCD40L), matrix metalloproteinase 9 (MMP-9) and pregnancy-associated plasma protein A (PAPP-A) were determined by ELISA. Serum levels of sCD40L and MMP-9 in patients of unstable plaques group, unruptured plaques group and rupture plaques group were all significantly enhanced compared to individuals of stable plaques group (SCD40L: χ(2) = 6.45, 12.04 and 16.23, P < 0.01; MMP-9; F = 2.55, 5.10 and 4.69, P < 0.05). Serum levels of PAPP-A in patients of unstable plaques group and rupture plaques group were all significantly enhanced compared to individuals of stable plaques group (χ(2) = 11.71 and 13.55, P < 0.05). Serum levels of PAPP-A in patients of rupture plaques group were significantly enhanced compared to individuals of unruptured plaques group (χ(2) = 13.19, P = 0.000). sCD40L ≥ 673.22 ng/L (OR = 22.47, 95%CI: 2.11 - 239.81, P = 0.010), MMP-9 ≥ 84.09 µg/L (OR = 10.01, 95%CI: 1.74 - 57.78, P = 0.010) and PAPP-A ≥ 0.101 µg/L (OR = 14.29, 95%CI: 2.69 - 75.90, P = 0.002) were all significantly correlated with the vulnerability of carotid plaques. There appear to be a relationship between the serum levels of sCD40L, MMP-9 and PAPP-A and the stability of carotid plaques in patients with carotid plaques. High serum levels of the above-mentioned markers may indicate that the plaques were vulnerable or ruptured.

Recently it has been reported that the lipid core area and the fibrous cap thickness cannot be deduced from the stenotic ratio. However, there is no comparative study between yellow and white plaques. This study assessed the precise characterization of yellow and white plaques using angioscopy. We observed 198 segments of coronary from autopsy artery using angioscopy, then 46 yellow plaque lesions and 61 white plaque lesions of atheroma were excised and prepared for pathological examination. The stenotic ratio, the plaque area (PA), the lipid core size as a percentage of total vessel area (%C), and the minimum fibrous cap thickness (FCt) were measured and compared between yellow and white plaque groups. In this study, the stenotic ratio and the PA were significantly larger in the white plaque group (p<.001). The FCt was significantly thinner in the yellow plaque group (58±18 µm vs. 648±356 µm p<.0001). There was no correlation between the stenotic ratio and the %C in the whole cases (r=.22). Although it was the same in the white plaque group (r=.13), significant correlation between them was shown in the yellow plaque group (r=.64). No significant correlation was observed between the stenotic ratio and the FCt in each plaque group. We concluded that a yellow plaque with moderate stenosis could be diagnosed as a vulnerable plaque by the combination of coronary angiography and angioscopy.

Although rupture of thin-cap fibroatheroma (TCFA) underlies most myocardial infarctions, reliable TCFA identification remains challenging. Virtual-histology intravascular ultrasound (VH-IVUS) and optical coherence tomography (OCT) can assess tissue composition and classify plaques. However, direct comparisons between VH-IVUS and OCT are lacking and it remains unknown whether combining these modalities improves TCFA identification. Two hundred fifty-eight regions-of-interest were obtained from autopsied human hearts, with plaque composition and classification assessed by histology and compared with coregistered ex vivo VH-IVUS and OCT. Sixty-seven regions-of-interest were classified as fibroatheroma on histology, with 22 meeting criteria for TCFA. On VH-IVUS, plaque (10.91±4.82 versus 8.42±4.57 mm(2); P=0.01) and necrotic core areas (1.59±0.99 versus 1.03±0.85 mm(2); P=0.02) were increased in TCFA versus other fibroatheroma. On OCT, although minimal fibrous cap thickness was similar (71.8±44.1 μm versus 72.6±32.4; P=0.30), the number of continuous frames with fibrous cap thickness ≤85 μm was higher in TCFA (6.5 [1.75-11.0] versus 2.0 [0.0-7.0]; P=0.03). Maximum lipid arc on OCT was an excellent discriminator of fibroatheroma (area under the curve, 0.92; 95% confidence interval, 0.87-0.97) and TCFA (area under the curve, 0.86; 95% confidence interval, 0.81-0.92), with lipid arc ≥80° the optimal cut-off value. Using existing criteria, the sensitivity, specificity, and diagnostic accuracy for TCFA identification was 63.6%, 78.1%, and 76.5% for VH-IVUS and 72.7%, 79.8%, and 79.0% for OCT. Combining VH-defined fibroatheroma and fibrous cap thickness ≤85 μm over 3 continuous frames improved TCFA identification, with diagnostic accuracy of 89.0%. Both VH-IVUS and OCT can reliably identify TCFA, although OCT accuracy may be improved using lipid arc ≥80° and fibrous cap thickness ≤85 μm over 3 continuous frames. Combined VH-IVUS/OCT imaging markedly improved TCFA identification.

Frequency-domain optical coherence tomography (FD-OCT) is a promising intracoronary imaging technique to study atherosclerosis. Indeed, its unprecedented spatial resolution allows the assessment of fibrous cap thickness, lipid pool and features of plaque vulnerability. Aim of this study was to determine the reproducibility of the in vivo FD-OCT measurements of lumen area and plaque components in serial studies. Twenty-six patients undergoing FD-OCT assessment of intermediate lesion during coronary angiography were included in this study. FD-OCT pullbacks were acquired twice from the same coronary segment at interval of 5 min without additional intervention and analyzed off-line at an independent imaging core laboratory. Lumen diameter (LD), lumen area (LA), fibrous cap (FC) thickness and lipid pool (LP) arc extension measurements were compared in 440 matched frames. Both the per-segment and per-frame analyses showed excellent correlation coefficients for the inter-pullback comparisons for all parameters explored (R > 0.95 and p < 0.001 in all cases). Accordingly, the Bland-Altman estimates of bias showed non-significant differences in the inter-pullback comparisons at all levels. Per-frame analysis showed a slightly variations of LA in 45.8% of cases with changes greater than 2% likely related to different phases of cardiac cycle. Nevertheless, nor FC thickness or circumferential arc of LP were affected by LA changes during serial FD-OCT acquisition. This study showed an excellent reproducibility of lumen and plaque component measurements obtained with FD-OCT in vivo. Thus, this intracoronary imaging technique could be used to assess atherosclerosis progression and describe accurate plaque evolution in repeated serial studies.

Relationship between Carotid Artery Remodeling and Plaque Vulnerability with T1-Weighted Magnetic Resonance Imaging

ObjectivesThis study was designed to investigate the relationship between intravascular ultrasonic plaque morphology and quantitative acoustic densitometry by integrated backscatter (IBS) of carotid plaque in patients with coronary artery disease.MethodsIntravascular...

This study aimed to demonstrate the effectiveness of spectral photon-counting CT (SPCCT) in quantifying fibrous cap (FC) thickness, FC area, and lipid-rich necrotic core (LRNC) area, in excised carotid atherosclerotic plaques by comparing it with histopathological measurements. This is a single-center ex vivo cross-sectional observational study. Excised plaques of 20 patients (71 +/- 6 years; 13 men), obtained from carotid endarterectomy were scanned with SPCCT using standardized acquisition settings (120kVp/19μA; 7-18keV, 18-30 keV, 30-45 keV, 45-75 keV, and 75-118 keV). FC thickness, FC area, and LRNC area were quantified and compared between high-resolution 3D multi-energy CT images and histopathology using the Wilcoxon signed-ranks test and Bland-Altman analysis. Images were interpreted twice by two radiologists separately, blinded to the histopathology; inter- and intra-rater reliability were assessed with the intra-class correlation coefficients (ICC). FC thickness and FC area did not show significant differences between the SPCCT-derived radiological measurements versus the histopathological measurements (p value range 0.15-0.51 for FC thickness and 0.053-0.30 for FC area). For the LRNC area, the p value was statistically non-significant for reader 1 (range 0.36-0.81). The Bland-Altman analysis showed mean difference and 95% confidence interval for FC thickness, FC area, and LRNC area, 0.04 (-0.36 to 0.12) square root mm, -0.18 (-0.34 to -0.02) log10 mm2 and 0.10 (-0.088. to 0.009) log10 mm2 respectively. The result demonstrated a viable technique for quantifying FC thickness, FC area, and LRNC area due to the combined effect of high spatial and energy resolution of SPCCT. • SPCCT can identify and quantify different components of carotid atherosclerotic plaque in ex vivo study. • Components of atherosclerotic plaque did not show significant differences between the SPCCT-derived radiological measurements versus the histopathological measurements.

Correlation between Acute Coronary Syndrome Classification and Multi-detector CT Characterization of Plaque

This research was aimed at exploring the application value of optical coherence tomography (OCT) images under adaptive segmentation algorithm in the early diagnosis of coronary heart disease (CHD). Eighty-two patients with CHD were included, who were to undergo coronary angiography (CAG) to confirm their condition. According to the diagnostic criteria of CHD in the American Coronary Artery Surgery Study (CASS), the patients were divided into the stable plaque group (41 cases) and unstable plaque group (41 cases). Besides, 20 healthy volunteers were selected as the control group, and all of them underwent OCT scans. On the basis of a fourth-order partial differential equation (PDE) and active contour (AC) model, a novel adaptive image segmentation algorithm PDE-AC was constructed and used for OCT image processing. No significant difference was found in general clinical data and serological indicators in the control group compared to the other two groups (P > 0.05). The lipid plaque length, degree of stenosis, and lipid pool angle, macrophages and intimal erosion, and plaque fissure in the unstable plaque group were highly greater than those in the stable plaque group. The fibrous cap thickness (FCT) was significantly thinner than that in the stable plaque group (P < 0.05). The diagnostic sensitivity, specificity, and accuracy of OCT under PDE-AC algorithm for CHD (91.53%, 84.08%, and 95.38%) were markedly higher than those of single OCT (83.46%, 75.11%, and 88.02%) (P < 0.05). In summary, OCT images under PDE-AC algorithm did better than simple OCT images in the diagnosis of CHD. Lipid plaque length, degree of stenosis, and lipid pool angle, macrophage and intimal erosion, plaque fissure, and FCT were important indicators for judging plaque stability, having the better clinical application value.

Compared with intravascular ultrasound (IVUS), optical coherence tomography (OCT) has relative merits and demerits for detecting plaque characteristics. It remains unknown whether the IVUS and OCT evaluations of plaque progression/regression are consistent. We sought to analyse the correlations between IVUS and OCT evaluations of plaques at single time points, and compare temporal changes in the IVUS and OCT data. Eighty-eight lipid-rich plaques from 65 patients with coronary artery disease were analysed with IVUS and OCT at baseline and 12-month follow-up. Fibrous cap thickness on OCT was negatively correlated with total atheroma volume on IVUS (r = -0.28, P = 0.009), but not with percent atheroma volume (P = 0.84). Changes on OCT were not significantly correlated with changes on IVUS. Plaques that showed progression, regression, or no change on IVUS showed no differences in terms of changes in the OCT parameters fibrous cap thickness (P = 0.199), maximum lipid core arc (P = 0.755), mean lipid core arc (P = 0.936), and lipid index (P = 0.91). The incidence of thin-cap fibroatheroma (TCFA) was similar among the above three plaque groups at baseline (P = 0.79) and follow-up (P = 0.609). Although fibrous cap thickness on OCT was negatively correlated with plaque size on IVUS at single time points, changes in OCT parameters were not correlated with changes in IVUS measures over time. Lesion progression/regression on IVUS was not associated with changes in OCT parameters (fibrous cap thickness, lipid core arc, lipid index, and TCFA).

Background— Positive arterial remodeling and thin fibrous cap are characteristics of rupture-prone or vulnerable plaque. The natural course of the fibrous cap thickness and the relationship between serial arterial remodeling and changes in fibrous cap thickness are unknown. Therefore, the purpose of this study was to evaluate the relationship between changes in fibrous cap thickness and arterial remodeling by using optical coherence tomography (OCT) and intravascular ultrasound (IVUS) during 6-month follow-up. Methods and Results— Both IVUS and OCT examinations were performed on 108 vessels from 36 patients with ischemic heart disease who underwent percutaneous coronary intervention. Fifty-eight fibroatheromas were selected from 82 nonsignificant, nonculprit lesions (angiographic diameter stenosis, 25% to 75%; plaque burden, &gt;40% by IVUS). Fibroatheroma was defined by OCT as lipid-rich plaque in &gt;1 quadrant that has lipid. Thickness of the fibrous cap was measured by OCT. IVUS and OCT examinations were repeated at 6-month follow-up. Serial changes and relationships between IVUS indices and fibrous cap thickness were investigated. Overall, fibrous cap thickness (98.1±38.9 to 96.9±44.5 μm) as well as IVUS indices did not change significantly within 6 months. The percent changes in fibrous cap thickness correlated negatively and significantly ( r =−0.54; P &lt;0.0001; generalized estimating equation adjusted, r =−0.42; P =0.001) with the percent changes in external elastic membrane cross-sectional area. Conclusions— Arterial remodeling is related to changes in fibrous cap thickness. Positive arterial remodeling is not only an adaptive process, but also related to thinning of the fibrous cap.

Plasma trimethylamine N-oxide is associated with vulnerable plaque characteristics in CAD patients as assessed by optical coherence tomography